1985 Chevrolet Truck Gas Gauge Pegs

1985 CHEVROLET TRUCK
Avatar
BAREFOOTBOB88
  • MEMBER
  • 60 POSTS
I just recently bought a old beater truck for $175 dollars. It runs great, but I have to guess how much gas I have by using the old slosh-and-listen technique. This truck has two fuel tanks. When I switch the tanks the one tank that doesn't work reads correctly on the guage. On the tank that does work the guage pegs itself way past the full mark.Quite annoying. I checked all the grounds just after I bought the truck and everything was in good shape. Should I replace the guage? What else could it be?
Jun 3, 2006 at 1:09 AM
Advertisement
Avatar
SYNCRAIT
  • ✓Experienced Mechanic
  • 235 POSTS
its going to be the sending unit inside the tank you might be better off taking both tanks apart and piecing them back together to make one functional tank, you might also try just checking the electrical connections and look for severed wires from atop the tank
good luck
Apr 21, 2021 at 5:36 AM
Avatar
BAREFOOTBOB88
  • MEMBER
  • 60 POSTS
thanks. I'll try it.
Apr 21, 2021 at 5:36 AM
Avatar
TWEBB101
  • MEMBER
  • 183 POSTS
Hey, I’ve got a similar issue on my 1984 Chevrolet C20. Tried two different gauges, both read empty. The newest gauge “dances” when the gas moves around. Bad sending unit as well?
Video (Click to enlarge)
Attached Media
Jan 8, 2022 at 6:16 AM
Avatar
KASEKENNY
  • ✓Experienced Mechanic
  • 18,907 POSTS
Yeah. Most likely this is a sending unit. The way to confirm this is to check the voltage coming from the sender.

https://www.2carpros.com/articles/how-to-check-wiring

Basically, if you monitor it while the key is on, and you are putting fuel in the tank from just a gas can you should see the voltage change.

My guess is it will not and that means the gauge is just showing what the sender is telling it and replace the sender.

Unfortunately, the manual does not have much info on this, but I attached what it does have.
Images (Click to enlarge)
Attached Media
Attached Media
Jan 13, 2022 at 8:57 AM
🔧 Tools & Auto Repair Parts
Find automotive tools, diagnostic equipment, and replacement parts for your next repair.
Shop on Amazon →
Paid affiliate link. As an Amazon Associate, we earn from qualifying purchases.

Suggested Repair

Suspect the in-tank sending unit rather than the gauge. Inspect connections and wires at the top of the tank for damage. Confirm by monitoring sender voltage with the key on while adding fuel; if voltage does not change, replace the sending unit. Parts from both tanks can be combined if needed to make one working tank.

Conversation Summary

The owner of a 1985 Chevrolet truck with two fuel tanks said the gauge reads correctly on the nonworking tank but pegs past full on the working tank. Grounds had already been checked. An expert blamed the in-tank sending unit and suggested checking connections and wires, or combining parts from both tanks. A later commenter with a 1984 Chevrolet C20 had gauges that read empty or moved with fuel slosh; the expert again pointed to the sending unit and recommended a sender voltage check while adding fuel.

Related Repair Questions

Add a reply
Join 2CarPros for free, one of the most advanced car repair communities on the internet. From first-time drivers to seasoned mechanics, everyone is welcome to reply, share details, and get better answers. You can add a temporary image or video first; uploads are limited to 20 MB.

Ask a new question

Frequently Asked Problems for This Vehicle